Motion converting mechanism



Dec. 27, 1955 1.. MIFFLIN MOTION CONVERTING MECHANISM Filed Nov. 19, 1951 INVENTOR. [0 flll'fl 11V United States Patent 0 MOTION CONVERTING MECHANISM- Leo Mifilin, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application November 19, 1951, Serial No. 257,091 4 Claims. (Cl. 74-10.85)

This invention relates in general to an adjusting means for a slug tuned coil and in particular to means for obtaining a desired frequency versus shaft position characteristic.

Slug tuned coils are used as variable inductances and it has been found desirable in many cases to vary the slug relative to the coil by attaching it to a lead screw. Screws are cut with a constant pitch so that as the lead screw rotates the slug advances at a constant rate. The slug movement versus inductance change of the coil is not linear, however, and various methods have been derived for compensating for the nonlinearity. For example, see the patent to Hunter, 2,468,071 which issued April 26, 1949. This patent illustrates a number of washers which are adjustable to allow the slug to move at a nonlinear rate as the lead screw is rotated.

It is an object of this invention to provide means for adjusting the tuning characteristics of a slug tuned coil.

Another object of this invention is to provide a tuning corrector for a variable inductance.

Further objects, features and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which;

Figure 1 is a sectional view of the slug tuned coil of this invention;

Figure 2 is an end view of the corrector assembly;

Figure 3 is a sectional view of the corrector assembly taken on line 3-3 of Figure 2; and,

Figure 4 is a side view of the corrector assembly.

As shown in Figure 1, this invention relates to a slug tuned coil which has a coil 10 that is wound about a form 11. The form 11 is hollow so as to receive a slug 12 therethrough. The slug may be pressed powdered iron, for example.

The coil form 11 is mounted on a base plate 13 and a longitudinal tuning shaft 14 is rotatably supported by plate 13 in suitable bearings 16. Retainer rings 17 and 18 prevent the shaft 14 from moving transversely of the plate 13. A knob 19 is connected to the outer end of the shaft 14 and may be used for rotating the shaft.

The portion of the shaft which passes through the bearing 16 is not threaded, but the opposite end 21 is threaded for a substantial length. The core 12 is hollow and is threadedly received on the shaft 14 by means of a collar or travelling nut 22. A cam follower mechanism, designated generally as 23, is attached to the collar 22. The follower mechanism engages projections 24 on discs 26.

The discs or washers 26 are supported by a second end plate 27 which rotatably supports one end of the shaft 14.

Clamping rings 28 and 29 clamp the washers 26 together and lead screws 39 are threadedly received in the end plate 27 which is held to the base plate 13 by standolfs 32. The discs 26 are held in axial alignment by guide members 33 spaced about their periphery, as for example, 120 degrees apart. Spacer washers 34 are mounted between each of the washers 26. The washers 26 are formed with external projections 36 to allow them to be adjusted radially when the screws 30 are loosened.

The cam follower, designated generally as 23, is best shown in Figure 2 and comprises a first extending memher 37 which carries a roller 38 at its outer end. it is attached to one end of collar 22. A second roller 39 is supported from the main body portion of the cam follower by lever arm 41. A spring 42 spring biases the lever arm 41 toward internal projections 24 formed on the discs 26.

The shaft 14 is threadedly received by the member 23. The slug 12 is hollow and moves with member 23. The projections 24, as best shown in Figure 1, are received between the rollers 38 and 39 and as the shaft 14 is rotated the slug 12 will move longitudinally relative to the coil 10 and at a rate dependent on the shape of the curve formed by the projections 24.

For example, if the projections 24 are in a straight line parallel to shaft 14, the movement of the slug 12 will be linear with reference to rotation of the shaft 14. However, if the projections 24 are adjusted to form a curve, as for example, as shown in Figure 4, the movement of the slug 12 will depend upon the shape of the curve as well as the rotation of the shaft 14.

This operation is readily understood from a consideration of the relative motion between the lead screw or driving member 21 of shaft 14 and the travelling not or driven member 22 which supports slug 12. Since the shaft 14 and the travelling nut 22 are provided with threads of constant pitch, the translatory displacement of the slug 12 with respect to the shaft 14 is directly proportional to the relative angular displacement between these two members. Relative angular displacement is produced by rotation, with respect to some reference body such as support 13, of the shaft 14 or the travelling nut 22 and, of course the net angular displacement is the algebraic sum of the component displacements.

Assume, for example, that the shaft 14 is provided with a right hand screw thread and the nut 22 has a corresponding thread. Consider that the rotational direction of the shaft 14 and the rotational direction of the nut 22 which causes slug 12 to advance toward the coil 10 both have a positive algebraic sign. If the shaft 14 is rotated one revolution clockwise and the travelling nut 22 is rotated one revolution counterclockwise, the relative angular displacement is two revolutions. Similarly, rotation of shaft 14 one revolution clockwise with simultaneous rotation of travelling nut 22 one-half revolution clockwise produces a relative angular displacement of one-half revolution. In the first case rotation of shaft 14 through one revolution produces a translatory displacement of nut 22 proportional to two revolutions relative angular displacement; in the second case the same rotation of shaft 14 produced a translatory displacement of nut 22 proportional to one-half revolution of relative angular displacement.

Thus, it is apparent that the translatory displacement of the nut 22 (and, therefore, the slug 12) can be made a non-linear function of the rotation of shaft 14 by causing concurrent rotation of nut 22. This concurrent rotation of the travelling nut 22 is produced by the cam follower assembly 23 attached thereto which is driven by the cam comprising projections 24. Since the translatory displacement of the nut 22 is a function of the relative rotation between shaft 14 and nut 22, and the rotation of nut 22 is determined by the shape of the cam, it is apparent that the translatory movement of the nut 22 together with the slug 12 is a predetermined function of the rotation of shaft 14. The functional relation is determined by the shape of the cam.

The shape of the curve may be varied by loosening the screws 30 and moving the projections 36 until the desired inductance is obtained for the particular shaft position. The projections 36 may be moved manually, and after the inductance versus core travel has been adjusted for the entire tuning range the screws 30 may be tightened and the apparatus is ready for use. The curve formed will be a smooth one due to the nature of the problem and the follower mechanism will easily follow the curve.

it is to be realized that the apparatus of this invention allows accurate adjustment of each individual tuner so that the overall tolerance in manufacturing need not be kept so high. This decreases cost and also allows control of the tuning characteristic so as to obtain an accuracy not previously possible.

It is to be noted that the projections 24 may be varied between limits of 0 and 120 degrees or if even more correction is needed, the spacing between guide members 33 may be increased.

Although this invention has been described with respect to a particular embodiment thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

, I claim:

1. A motion converting mechanism comprising, a base member, a longitudinal driving shaft supported by said base member, a threaded portion on said shaft, a driven member threadedly received on the threaded portion, an adjustable disc assembly formed with internal projections, and a cam follower attached to said driven member and engaging the projections of said disc assembly.

2. A motion converting mechanism comprising, a pair of end plates connected by standoffs, a longitudinal shaft rotatably supported between said end plates, a threaded portion on saidshaft between said end plates, a member threadedly received on said portion, a plurality of discs supported by one of said plates about the shaft, said discs each formed with an internal projection, and a cam follower mechanism attached tosaid member and engageable with the projections of said discs so that i when the shaft is rotated the translatory motion of the member will be dependent upon the shape of the curve formed by said projections.

3. A mechanism for controlling the translatory motion of a driven member with respect to a fixed member comprising, an end plate, said fixed member supported by said end plate, a shaft extending through said end plate and rotatably supported thereby, a threaded portion on said shaft adjacent said fixed member, a threaded driven member received on said threaded portion, a cam follower mechanism attached to said driven member, a plurality of rings enclosing said driven member, each of said rings formed with an internal projection releasable locking means engaging said rings and said plate, and means for adjusting the position of said internal projections, said cam follower mechanism provided with a pair of spaced arms engageable with opposite sides of said internal projections and resilient means urging said arms together to control the translatory motion of said driven member.

4. A motion converting mechanism comprising a support member, a rotatable input shaft including a threaded driving member mounted on said support member, a translatable output member including a threaded driven member in engagement with said driving member, means for producing limited rotation of said driven member concurrently with rotation of said driving member for causing translation of said output member to be a nonlinear function of the rotation of said shaft comprising a cam assembly including plural axially aligned rings coaxial with said shaft each having a radially extending internal projection, said rings being individually rotatable for positioning said projections to define a desired curve, and. a cam follower connected with said output member and engaging said projections for imparting rotary motion to said driven member during axial motion of said driven member.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,071 Hunter Apr. 26, 1949 2,505,791 Rennick May 2, 1950 

